This disclosure relates to a level shift circuit that outputs an output signal at a voltage different from the voltage of an input signal.
As a circuit that on-off drives a semiconductor switching element that configures the upper arm of a bridge circuit for electric power inverse conversion (conversion from a direct current to an alternating current) of a PWM inverter and the like used as a motor driver and the like, a so-called level shift circuit that does not perform potential insulation by a transformer, a photocoupler, and the like has been recently used for cost reduction.
In addition, the level shift circuit has been used in a nonvolatile memory operated at various power supply voltages.
However, when the typical level shift circuit that converts a low voltage signal to a high voltage signal is used for these applications, there are various problems.
For example, when the motor is PWM controlled, a delay difference is caused between the rising time and the falling time of the signal in the typical level shift circuit. Due to this, the pulse width is different between the input and the output, and consequently, there is a problem that precise control is difficult.
In addition, in the typical level shift circuit of the nonvolatile memory, there is a problem that the circuit area becomes large to increase the cost.
For coping with the problems, to easily control the pulse width and to reduce the circuit area, a level shift circuit that uses an RS flip flop circuit to convert a low voltage signal to a high voltage signal is proposed (see U.S. Pat. No. 3,635,975).
In addition, a pulse generation circuit that generates a pulse signal inputted to the RS flip flop circuit used for the level shift circuit is proposed (see U.S. Pat. No. 4,702,261).